Zcash is built on top of the same technologies that powers Bitcoin, it was forked from Bitcoin.

While it has some issues like mining pool centralization, dev fees, and optional privacy, it's zk-Snarks privacy is amongst the most private protocol there is equal to or greater than Monero's privacy.

If Bitcoin implemented zero knowledge, or other privacy mechanisms, it would probably make Bitcoin extremely more valuable as a currency honestly.

Bitcoin could easily displace Zcash, and make it irrelevant if it wanted to.